Serum osteocalcin in rheumatoid arthritis and other inflammatory arthritides: relation between inflammatory activity and the effect of glucocorticoids and remission inducing drugs.

Osteocalcin, a vitamin K dependent protein synthesised by osteoblasts, was measured in serum by radioimmunoassay in patients with rheumatoid arthritis (n = 36) and seronegative spondyloarthropathies (n = 23). The serum osteocalcin levels were decreased in both patient groups compared with the levels measured in age and sex matched healthy controls. We found no relation between serum osteocalcin and the disease duration or inflammatory activity of the patients who were without drug treatment at the first examination. After administration of glucocorticoids (20 mg prednisolone a day) circulating osteocalcin decreased significantly after one week of treatment. During gradual reduction of the steroid dosage osteocalcin returned to pretreatment values. Treatment with non-steroidal anti-inflammatory drugs (NSAIDs) did not influence circulating osteocalcin. During treatment with chloroquine or penicillamine serum osteocalcin increased significantly, concomitant with a reduction of the acute phase reactants. Controversy persists about the abnormality of bone turnover in rheumatic diseases, but our data suggest that the overall bone turnover is decreased in patients with rheumatoid arthritis and other inflammatory arthritides.